Recently developed microdisplays can provide large format, high resolution color pictures and streaming video in a very small form factor. One use for such displays is in a head mounted display (HMD) apparatus worn on the user's face or head similar to a pair of eyeglasses or headphones. The electronics enclosed in such devices have become extremely sophisticated and can now include integrated data processors, wireless interfaces, and other input devices such as head tracking accelerometers, cameras, voice recognition circuits and software and other components.